Have you seen the
Disney movie, Black Hole, from 1979? It was typical Disney fare;
clueless good guy, camouflaged bad guy, comic relief characters… And all the
action happened on a ship that sat in space, just outside the ‘point of no
return’ of a Black Hole, which was depicted as a whirlpool of light.
Even then, I knew a
black hole was ‘a region of space having a gravitational field so intense that
no matter or radiation can escape.’ So that depiction of a black hole bothered
me. If light can’t escape, then the black hole would not appear as a whirlpool
of light. It should be black. Even light from stars beyond the black hole shouldn’t
be seen; it would be bent and swallowed before it reached the observer. Right?
That’s what I was
thinking, anyway.
These days, the idea of
a Black Hole is not quite so… black and white.
NASA says a black hole
is a place in space where the gravity is so intense, light cannot escape. In
the same article, they say that if a
black hole is located close to a star, high-energy (invisible) light is
released. I suppose this is a special case, but I think they should have
started by saying no visible light
can escape.
Another NASA webpage
states that black holes cannot be seen, because (visible) light cannot escape.
But anything in the vicinity is effected. Dust bits will fall into the black
hole, getting closer and closer until they hit that ‘point of no return’, when
the light reflecting off them can no longer escape. The gravity will tug at any
stars and planets in the area, making them wobble as they try to resist. Stars
might even be pulled apart, and slurped up. As the star matter accelerates
toward the hole, it emits x-rays, which can be detected by the proper
equipment.
But something can and
does escape from black holes, in a way. Some matter that is falling into a
black hole ricochets off the event horizon (point of no return) instead of
going through it. It bounces away at a speed so great, the jet of material can
be detected relatively easily.
If that’s not enough
for you, then consider a super-black hole that spins really, really fast. This
spin creates a charge-separated magnetosphere, which forms parallel electrical
charges around the poles. Particles accelerate to very close almost the speed
of light and are thrown out into space as gamma radiation bursts. Bursts have
been observed from the massive black hole at the center of Galaxy IC310.
However, the description of how they are created is just a theory, since no one
can see inside the event horizon to see what’s going on.
So, Black Holes are
pretty black, unless something is escaping.
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